Building Envelope & Energy Audit Flashcards

A commissioning professional is reviewing flashing details at a through-wall condition in a brick veneer assembly. Which fundamental drainage plane principle must be maintained to prevent water intrusion?

Answer: Flashing must lap over the drainage plane below and direct water to the exterior with end dams at terminations

Effective through-wall flashing must maintain continuity with the drainage plane, lap correctly to direct water outward, and include end dams to prevent water from running off flashing ends back into the wall cavity.

During an energy audit, a commissioning professional calculates that a building's infiltration rate is 0.35 ACH (air changes per hour) at natural pressure. Using the Lawrence Berkeley National Laboratory (LBNL) infiltration model, what fractional relationship exists between blower door ACH50 and natural ACH?

Answer: Natural ACH ≈ ACH50 ÷ 20

The common rule of thumb from the LBL infiltration model is that natural infiltration (ACH) approximately equals ACH50 divided by 20 for typical US climates and building heights.

When a commissioning professional evaluates a green roof assembly as part of an energy audit, which thermal benefit is most accurately attributed to the vegetated layer?

Answer: Evapotranspiration cooling that reduces peak roof surface temperature and summer cooling loads

Green roofs primarily reduce cooling loads through evapotranspiration, which absorbs heat as plants release moisture, significantly lowering peak roof surface temperatures in summer.

A commissioning professional is assessing the dew point risk in a wall assembly in a hot-humid climate (Climate Zone 2A). Where should the vapor retarder be placed to minimize condensation risk?

Answer: On the exterior side of the wall sheathing (toward the exterior)

In hot-humid climates, the dominant vapor drive is from the hot-humid exterior toward the cooler conditioned interior, so vapor retarders should be placed toward the exterior to resist inward vapor diffusion.

A building envelope commissioning report identifies 'ghosting' patterns on exterior cladding visible in infrared imagery. What does this pattern most likely indicate?

Answer: Thermal bridging through wall studs or structural framing visible as heat loss patterns

Ghosting patterns in infrared images of exterior cladding reveal the regular spacing of wall framing members conducting more heat than insulation, making studs visible as warmer stripes on cold exterior surfaces.

During an ASHRAE Level III energy audit, a commissioning professional calibrates an energy model. Which method is used to validate the model against actual utility data?

Answer: Checking that simulated monthly energy use matches utility bills within ASHRAE Guideline 14 tolerances (CV-RMSE ≤15%, NMBE ≤5%)

ASHRAE Guideline 14 requires calibrated simulation models to achieve CV-RMSE of 15% or less and NMBE of 5% or less when comparing simulated to actual monthly utility consumption.

A commissioning professional reviewing energy audit findings for a large warehouse notes that the measured lighting power density (LPD) is 1.4 W/ft². The current ASHRAE 90.1 allowance for warehouses is 0.66 W/ft². What percentage energy reduction is achievable from lighting alone if the building is brought into compliance?

Answer: Approximately 53% reduction

Reducing from 1.4 W/ft² to 0.66 W/ft² represents a reduction of 0.74 W/ft², which is (0.74 ÷ 1.4) × 100 ≈ 53% reduction in lighting energy use.